摘要
丽水凹陷东部边界WZ27-1井为东海陆架盆地钻穿新生代的少数钻井之一,依据录井资料显示其前新生代钻遇花岗岩。通过对其底部岩屑样品岩石薄片研究发现,矿物成分主要为石英和长石,呈半自形或它形粒状分布,具有典型的花岗岩结构;结合对样品的肉眼观察,以及地震剖面和测井解释资料,进一步确认该井底部所钻遇地层为浅层中酸性花岗岩,或具有一定规模的分布。同时运用锆石U-Pb定年方法,厘定该花岗岩的形成时代,结果显示该岩体主体形成于晚三叠世-早侏罗世（194-243 Ma±）,大致可分为205 Ma±和220 Ma±两期。上述结果,首次揭示在东海陆架盆地丽水凹陷内发育有印支期基底花岗岩体,具有重要的构造指示意义。结合我国东南陆域及琉球岛弧同期岩体发育特征及中生代沉积岩分布特点,认为东南陆域与东海陆架盆地在中生代处于同一基底之上,经历三期相同构造背景的转换。
Located near the eastern border of the Lishui Sag, well WZ27-1 is one of the few wells drilling through Cenozoic in the East China Sea shelf basin. According to the logging data, well WZ27-1 encountered pre-Cenozoic granite. The petrographic thin sections of debris samples in the bottom of the well show that the main mineral is quartz and feldspar, and the mineral is allotriomorphic or subhedral in the grainy distribution, so the sample has typical granite structure. Almost the entire debris sample looks like the granite, and based on the seismic profile and logging interpretation of the sample under the bottom of the border, the sample can be confirmed to be granite formed in the shallow and took a certain space. The zircon U-Pb aging experiments are used to get the age of the granite. The results show the rock was formed in Late Triassic-Early Jurassic（ 194 -243Ma ±） overall, and could be divided into two phases（205Ma± and 220Ma±）. This first discovery of Indosinian granite basement in the Lishui Sag of East China Sea shelf basin has important tectonic significance. After summarizing and analyzing characteristics of Early Mesozoic igneous rock and distribution feature of Mesozoic sediments in Southeast China and Ryukyu island arc, Southeast China and East China Sea shelf basins are considered on the same basement and experienced the same 3 phases of structural background switches during Mesozoic.
出处
《海洋通报》
CAS
CSCD
北大核心
2015年第6期675-687,共13页
Marine Science Bulletin
基金
国家科技重大专项(2011ZX05023)
关键词
东海陆架盆地
丽水凹陷
基底性质
锆石定年
中生代花岗岩
East China Sea shelf basin
Lishui Sag
basement characteristics
zircon aging
Mesozoic granite
